The move, included in a little-noticed provision of the 2006 National Defense Authorization Act passed last month, marks a legislative victory for Defense Secretary Donald H. Rumsfeld, who pushed hard for the new powers to deal with emergency situations.

But it has drawn warnings from foreign policy specialists inside and outside the government, who say it could lead to growth of a separate military assistance effort not subject to the same constraints applied to foreign aid programs that are administered by the State Department. Such constraints are meant to ensure that aid recipients meet certain standards, including respect for human rights and protection of legitimate civilian authorities.

"It's important that diplomats remain the ones to make the decisions about U.S. foreign assistance," said George Withers, a senior fellow at the Washington Office on Latin America and a former staff member on the House Armed Services Committee. "They can ensure such decisions are taken in the broader context of U.S. foreign policy."

Many lawmakers, too, were initially cool to Rumsfeld's request. The Armed Services committees in both the House and Senate declined to write the provision into their original defense authorization bills, citing concerns about a lack of jurisdiction and an absence of detail about where the money would be spent.

But the Pentagon pressed its case, with senior commanders joining top officials in weighing in with reluctant members.

"This was the most heavily lobbied we've been by the Pentagon in the several years I've been here," said one Senate staff member. "They really, really wanted this."

Issandr El Amrani is a Cairo-based writer and consultant. His reporting and commentary on the Middle East and North Africa has appeared in The Economist, London Review of Books, Financial Times, The National, The Guardian, Time and other publications. He also publishes one of the longest-running blog in the region, www.arabist.net.